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//usr/lib64/python2.7/site-packages/mx/BeeBase/FileLock.py
""" FileLock - Implements a file lock mechanism that does not depend on fcntl. Copyright (c) 1997-2000, Marc-Andre Lemburg; mailto:mal@lemburg.com Copyright (c) 2000-2011, eGenix.com Software GmbH; mailto:info@egenix.com See the documentation for further information on copyrights, or contact the author. All Rights Reserved. """ from mx.Misc.ExitFunctions import ExitFunctions import os,exceptions,time # Version __version__ = '1.0' # Get fully qualified hostname def _fqhostname(hostname=None,default=('localhost','127.0.0.1')): """ Returns fully qualified (hostname, ip) for the given hostname. If hostname is not given, the default name of the local host is chosen. Defaults to default in case an error occurs while trying to determine the data. """ try: import socket except ImportError: return default try: if hostname is None: hostname = socket.gethostname() ip = socket.gethostbyname(hostname) hostname = socket.gethostbyaddr(ip)[0] except socket.error: return default else: return hostname,ip hostname,ip = _fqhostname() ### Errors class Error(exceptions.StandardError): pass # Backward compatibility: FileLockError = Error ### File lock using symbolic links class SymbolicFileLock: """ Implements a file lock mechanism. The base class implements the locking mechanism using symbolic links. Note that since the mechanism does not use file system function calls this may not always work in the desired way. The lock is acquired per process, not per thread. Instancevariables: filename - file the lock applies to lockfilename - name of the lock file locked - indicator if the lock is in position (1) or not (0) """ # Do we hold the lock ? locked = 0 # Lock timeout in seconds (0 = never) locktimeout = 0 def __init__(self, filename): self.filename = filename self.lockfilename = filename + '.locked' self.locked = 0 # Avoid deadlocks ExitFunctions.register(self.unlock) def __del__(self): if self.locked: self.unlock(0) try: ExitFunctions.deregister(self.unlock) except: pass def lock(self,timeout=500,sleeptime=0.0001, sleep=time.sleep,Error=Error,time=time.time,error=os.error, hostname=hostname,ip=ip): """ Try to lock the file for this process, waiting timeout ms if necessary. Raises an exception if a timeout occurs. Multiple locking by the same process is not an error. Note that a non existent path to the file will also result in a timeout. If the lock is held by a process running on our host, a timeout will first invoke a check of the locking process. If it is not alive anymore, the lock is removed and granted to the current process. """ if self.locked: return lockfilename = self.lockfilename lockinfo = '%s:%i' % (hostname,os.getpid()) stop = time() + timeout * 0.001 # Localize these for speed islink=os.path.islink makelink=os.symlink readlink=os.readlink while 1: # These are rather time-critical if not islink(lockfilename): try: makelink(lockinfo,lockfilename) except error: # A non existent path will result in a time out. pass else: break sleep(sleeptime) if time() > stop: # Timeout... check whether it's a valid lock if not self.validate_lock(): continue host, locking_pid = self.lock_info() raise Error,\ 'file "%s" is locked by process %s:%i' % \ (self.filename, host, locking_pid) self.locked = 1 def unlock(self,sleeptime=0.0001, unlink=os.unlink,Error=Error,sleep=time.sleep,error=os.error): """ Release the lock, letting other processes using this mechanism access the file. Multiple unlocking is not an error. Raises an exception if the lock file was already deleted by another process. After having unlocked the file the process sleeps for sleeptime seconds to give other processes a chance to acquire the lock too. If the lock will only be used every once in a while by the process, it is safe to set it to 0. """ if not self.locked: return self.locked = 0 try: unlink(self.lockfilename) except error: raise Error,'file lock "%s" is already gone' % \ self.lockfilename # Give other processes a chance too if sleeptime: sleep(sleeptime) return 1 def has_lock(self): """ Returns the current state of the file lock: 1 - a lock exists, 0 - no lock exists. Note that in case a lock exists, this lock is not checked for being valid. """ if self.locked: return 1 if os.path.islink(self.lockfilename): return 1 return 0 def lock_info(self): """ Returns a tuple (hostname, PID integer) indicating the host and process id currently holding the lock. An Error is raised if no lock exists. """ try: host,locking_pid = os.readlink(self.lockfilename).split(':') except os.error,why: raise Error,\ 'file "%s" could not be locked: %s' % \ (self.filename,why) locking_pid = int(locking_pid) return (host, locking_pid) def validate_lock(self): """ Validates a lock on the file and return 1 for a valid lock, 0 for an invalid one. Note that it is only possible to check for valid locks which are owned by the same host. This method removes any invalid locks it may find. An Error is raised if no lock exists. """ # Check for lock timeouts if self.locktimeout: ctime = self.lock_time() if ctime < time.time() - self.locktimeout: # Timed out try: os.unlink(self.lockfilename) except os.error, why: # We probably don't have proper permissions. return 1 else: return 0 # Check process host, locking_pid = self.lock_info() if host != hostname: # Ok, then compare via IPs other_ip = _fqhostname(host, default=('???','???'))[1] samehost = (ip == other_ip) else: samehost = 1 if samehost: # Check whether the locking process is still alive try: os.kill(locking_pid, 0) except os.error, why: # It's gone without a trace... try: os.unlink(self.lockfilename) except os.error: # We probably don't have proper permissions. pass else: return 0 return 1 def lock_time(self): """ Returns a Unix time value indicating the time when the current lock was created. An Error is raised if no lock exists. """ try: ctime = os.lstat(self.lockfilename)[9] except os.error, why: raise Error,\ 'could not read file lock info for "%s": %s' % \ (self.filename, why) return ctime def remove_lock(self, unlink=os.unlink): """ Remove any existing lock on the file. """ self.locked = 0 try: unlink(self.lockfilename) except: pass def __repr__(self): return '<%s for "%s" at %x>' % (self.__class__.__name__, self.filename, id(self)) # Alias BaseFileLock = SymbolicFileLock ### File lock using directories class DirectyFileLock(BaseFileLock): """ This class implements a file lock mechanism that uses temporary directories for locking. See FileLock for documentation of the various methods. Thanks to Thomas Heller for this idea ! """ def lock(self,timeout=500,sleeptime=0.0001, sleep=time.sleep,Error=Error,time=time.time,error=os.error, hostname=hostname,ip=ip,mkdir=os.mkdir): if self.locked: return lockfilename = self.lockfilename lockinfo = '%s:%i' % (hostname,os.getpid()) stop = time() + timeout * 0.001 while 1: # These are rather time-critical try: mkdir(lockfilename) except error: # A non existent path will result in a time out. pass else: break sleep(sleeptime) if time() > stop: # Timeout... check whether it's a valid lock if not self.validate_lock(): continue raise Error,\ 'file "%s" is currently locked' % self.filename self.locked = 1 def unlock(self,sleeptime=0.0001, rmdir=os.rmdir,Error=Error,sleep=time.sleep,error=os.error): if not self.locked: return self.locked = 0 try: rmdir(self.lockfilename) except error: raise Error,'file lock "%s" is already gone' % \ self.lockfilename # Give other processes a chance too if sleeptime: sleep(sleeptime) return 1 def has_lock(self): if self.locked: return 1 if os.path.isdir(self.lockfilename): return 1 return 0 def validate_lock(self): # Check for lock timeouts if self.locktimeout: ctime = self.lock_time() if ctime < time.time() - self.locktimeout: # Timed out try: os.rmdir(self.lockfilename) except os.error, why: # We probably don't have proper permissions. return 1 else: return 0 return 1 def lock_info(self): """ Locking info is not available for DirectyFileLocks. A TypeError is raised in case this method is called. """ raise TypeError, \ '.lock_info() is not implemented for DirectyFileLocks' def lock_time(self): try: ctime = os.stat(self.lockfilename)[9] except os.error, why: raise Error,\ 'could not read file lock info for "%s": %s' % \ (self.filename, why) return ctime def remove_lock(self, rmdir=os.rmdir): self.locked = 0 try: rmdir(self.lockfilename) except: pass ### Generic file lock mechanism if hasattr(os, 'symlink'): FileLock = SymbolicFileLock else: FileLock = DirectyFileLock def _test(): #lock = SymbolicFileLock('test-lock') #lock = DirectyFileLock('test-lock') lock = FileLock('test-lock') starttime = time.time() try: for i in range(10000): print '%i\r'%i, lock.lock() time.sleep(i/100000.0) lock.unlock() #time.sleep(i/100000.0) except KeyboardInterrupt: lock.unlock() totaltime = time.time() - starttime print '%i lock/release cycles in %5.2f sec. = %i cycles/sec.' % \ (i, totaltime, i / totaltime) if __name__ == '__main__': _test()
